氧化应激可选择性诱导细胞的NKG2D配体的表达

目的 探讨氧化应激与细胞NKG2D配体表达的关系,分析氧化应激对NK细胞功能的影响。方法 加H2O2诱导培养的肿瘤细胞处于氧化应激状态。用RT-PCR、Real-time PCR和流式细胞仪等方法分析细胞多种NKG2D配体的表达。用CCK-8法检测NK92细胞对肿瘤细胞的杀伤活性。结果 氧化应激可诱导肿瘤细胞多种NKG2D配体的表达,不同的肿瘤细胞诱导表达的NKG2D配体不同;NKG2D配体表达上调可有效提高NK细胞的细胞毒活性,此效应可被抗NKG2D抗体所阻断。结论 NKG2D配体可能在机体的免疫应答中发挥正向的调节作用。     

MICA分子在NK细胞杀伤乳腺癌中的作用

目的 观察乳腺肿瘤细胞膜MHC Ⅰ链相关分子A(MHC class Ⅰ chain-related gene A,MICA)及血清中可溶性MICA表达,探讨MICA在NK细胞杀伤乳腺癌中的作用.方法 流式细胞术检测膜型MICA(mMICA)及NK细胞表面NKG2D表达,观察膜型MICA、可溶性MICA(sMIcA)对NKG2D表达的影响;免疫组织化学检测膜型MICA及可溶性MICA的表达及分布;抗体封闭法观察膜型MICA与NKG2D相互作用.结果 乳腺细胞膜型MICA在正常组织不表达,在良性肿瘤表达量为(38.5±7.5)%,恶性肿瘤表达量为(53.2±5.6)%.可溶性MICA含量在健康成年人为阴性,在乳腺良性肿瘤患者血清中含量(76.8±22.3)pg/mL,在恶性肿瘤患者中含量(205.36±71.27)pg/mL.经NKG2D或MICA抗体封闭后,NK细胞的杀瘤活性显著减弱.含可溶性MICA的血清可明显下调NKG2D的表达.结论 大部分乳腺肿瘤细胞膜都有MICA的表达,可作为乳腺肿瘤相关性抗原.膜型MICA与NKG2D的相互识别在介导NK细胞抗乳腺癌中起重要作用,而可溶性MICA通过下调NKG2D表达介导肿瘤免疫逃逸.     

白血病患者NK细胞表面NKG2D受体及其配体MICA/B的研究

目的:研究白血病患者NK细胞表面NKG2D受体及其配体MICA/B的表达,探讨白血病细胞逃逸NK细胞杀伤的机制.方法:采用流式细胞术检测NK细胞表面NKG2D受体和骨髓有核细胞表面MICA/B配体.结果:治疗前组和完全缓解组NKG2D受体的表达均较健康组低(P＜0.05);且完全缓解组低于治疗前组(P＜0.05);治疗前组和完全缓解组MICA/B配体的表达均低于增生性贫血组(P＞0.50);完全缓解组与治疗前组比较差异无显著性(P＞0.05).结论:白血病患者体内NKG2D-MICA/B介导的NK细胞功能受抑,这可能导致白血病细胞逃逸NK细胞的细胞毒作用;白血病化疗后完全缓解时其体内NKG2D-MICA/B介导的NK细胞功能仍未恢复,且较治疗前更低.     

板蓝根多糖促进NKG2D 配体表达增强NK 细胞对食管癌细胞的杀伤作用及机制研究

目的:研究板蓝根多糖(RIP)影响NK细胞对食管癌细胞杀伤作用的分子机制。方法:MTT法检测细胞增殖率,Western blot检测增殖相关蛋白CyclinD1、p21和p27的表达,ELISA法检测培养上清中IFN-γ和TNF-α的表达,流式细胞术检测NKG2D配体MICA、MICB、ULBP1和ULBP2的表达,钙黄绿素释放法(CARE-LASS)检测NK细胞对食管癌细胞的杀伤率。结果:RIP可促进NK-92细胞增殖,抑制食管癌Eca-109细胞增殖,且具有显著剂量依赖性。食管癌可促进NK细胞中TNF-α和IFN-γ的表达。RIP可促进食管癌细胞Eca-109中NKG2D配体MICA、MICB、ULBP1和ULBP2的表达,促进与食管癌细胞联合作用后NK细胞中TNF-α和IFN-γ表达,提高NK-92细胞对食管癌Eca-109细胞的杀伤活性。结论:RIP通过提高食管癌Eca-109细胞中NKG2D配体表达,促进NK-92细胞中TNF-α和IFN-γ表达,增强NK-92细胞对食管癌细胞的杀伤作用。     

三氧化二砷提高多发性骨髓瘤ARH-77细胞对NK细胞杀伤敏感性的研究

目的 研究三氧化二砷(arsenic trioxide,ATO)前后人多发性骨髓瘤ARH-77对NK细胞杀伤细胞敏感性的变化,并初步探讨其机制.方法 分别应用CCK-8法和台盼蓝染色法测算ATO对ARH-77细胞株的50%抑制量(IC50)和细胞活性;乳酸脱氢酶释放法检测ATO作用前后ARH-77细胞对NK细胞的杀伤敏感性.流式细胞仪检测ARH-77细胞表面NKG2D配体(MICA/B、ULBP1、ULBP2、ULBP3)和HLA-Ⅰ类分子表达以及ATO作用前后的细胞周期变化.结果 ATO对ARH-77细胞的IG50为5.0μmol/L.NK 细胞杀伤ATO作用前后ARH-77细胞的活性有显著差异(P＜0.05).ATO作用后,ARH-77细胞发生G1/S期阻滞,同时其表面MICA/B、ULBP1、ULBP3表达显著升高,二者之间差异有统计学意义(P＜0.05).ULBP2和HLA-Ⅰ类分子无明显变化(P＞0.05).结论 ATO能提高ARH-77细胞NKG2D配体(MICA/B、ULBP1、ULIBP3)表达;从而使其对NK细胞的杀伤敏感性增强.     

膜型/分泌型MICA对NK细胞受体NKG2D的相反调节效应及其对NK细胞受体谱的影响

目的　观察膜型和分泌型MICA对NK细胞受体表达的影响 ,以探讨NK细胞抗肿瘤活化机制及肿瘤细胞表达MICA分子的意义。方法　用MTT法测定人NK细胞系 (NK92 )的细胞毒活性 ;用RT PCR或FACS检测NK细胞受体 (NKG2D ,NKG2A B ,KIR2DL1,KIR2DS1)及NKG2D的识别配体MICA的表达。结果　肿瘤细胞表面的MICA分子可上调NKG2D的表达 ,下调抑制性受体NKG2A B和KIR2DL1的表达 ;而分泌型MICA (sMICA)分子对NKG2D及抑制性受体的表达均有抑制作用。结论　膜型MICA分子可上调NKG2D的表达 ,激发NK细胞对肿瘤细胞的细胞毒效应 ;分泌型MICA分子则通过降低NKG2D的表达下调机体的抗肿瘤免疫效应 ,肿瘤细胞分泌sMICA分子为肿瘤发生免疫逃逸的机制之一。     

结肠癌患者单核或树突状细胞MICA的表达及其与NK细胞活性的关联

目的:观察结肠癌患者单核或树突状细胞是否表达MHCⅠ类相关抗原A(MICA),并分析MICA+单核细胞的频率是否与患者体内NK细胞的活性相关联。方法:首先利用流式细胞仪检测MICA在外周血单核细胞和由单核细胞诱导而来树突状细胞(DCs)上的表达;并用IL-15和IFNα-刺激树突状细胞,观察MICA表达的变化;然后检测患者外周血NKG2D+、CD16+、CD69+NK细胞的频率及NK细胞的杀伤活性;最后分析MICA+单核细胞的频率是否与NK细胞表达NKG2D及其杀伤活性关联。结果:与健康个体相比,结肠癌患者MICA+单核细胞的频率无显著变化。未成熟DCs表达MICA,但受IL-15和IFNα-刺激后,结肠癌来源的DCs表面MICA的表达无显著上调。结肠癌患者外周血NKG2D+、CD69+NK细胞的频率显著降低,NK细胞的杀伤活性显著降低,而CD16+NK细胞的频率无明显变化。结肠癌患者MICA+单核细胞的频率与NK细胞表达NKG2D无明显关联,但与NK细胞杀伤靶细胞时CD107a的表达正相关。结论:结肠癌患者体内单核细胞表达MICA与NK细胞表达NKG2D无关,但高频率MICA阳性的单核细胞与NK细胞的抗肿瘤活性正相关。     

NKG2D配体在鼻咽癌细胞的表达及其对NK细胞杀伤活性的影响

NK细胞对靶细胞的杀伤活性与其细胞表面的受体和靶细胞表面的配体密切相关，NKG2D为NK细胞活化性受体，表达于所有的NK细胞表面，是介导NK细胞识别和溶解肿瘤细胞的主要活化性受体。NKG2D配体为MHCⅠ类链相关基因产物（MICA、MICB）及ULBPS（人巨细胞病毒UL16蛋白的结合蛋白ULBP1、ULBP2、ULBP3），NKG2D的配体在多种肿瘤细胞表达，其在鼻咽癌细胞的表达尚未见报道。本文通过流式细胞仪技术探讨其在鼻咽癌细胞CNE2的表达情况，并进一步分析其在NK细胞杀伤CNE2细胞中的作用。     

NKG2D配体的表达直接影响NK细胞对不同发育阶段DC的杀伤

目的:探讨NKG2D配体在不同发育阶段树突状细胞(DC)表面的表达及其对自然杀伤(NK)细胞杀伤活性的影响.方法:用细胞因子(rh IL-4、rhGM-CSF、TNF-α)体外诱导培养单核细胞来源的未成熟树突状细胞(iDC)和成熟树突状细胞(mDC)并鉴定形态和表型,免疫磁珠法分离纯化NK细胞.流式细胞术(FCM)检测iDC和mDC表面NKG2D配体MICA/B、ULBP1-3的表达.用LDH释放法检测NK细胞对iDC和mDC的杀伤活性以及抗NKG2D单克隆抗体(mAb)阻断NK细胞后的杀伤活性.结果:培养的iDC和mDC具有典型的细胞形态和免疫表型特征.iDC表面表达MICA、MICB、ULBP1、ULBP3,表达率分别为(32.39±8.30)%、(17.75±3.40)%、(26.71±6.48)%、(38.37±6.89)%;mDC表面表达MICA 、ULBP3,表达率分别为(7.82±2.67)%、(8.36±2.42)%,比iDC表面相应配体表达率低(P<0.01).各效靶比NK细胞对iDC的杀伤活性均比对mDC的杀伤活性高,差异有统计学意义(P<0.01).抗NKG2D mAb阻断NK细胞后对iDC杀伤活性比阻断前减弱(P<0.05);对mDC的杀伤活性与阻断前相比无统计学意义(P>0.05).结论:NKG2D配体在iDC表面表达高,介导了NK细胞对iDC的杀伤,而对mDC的杀伤无影响,是NK细胞对iDC选择性高杀伤的分子机制之一.     

同种异体NK细胞对人脐静脉内皮细胞ECV304的杀伤活性差异及分子机制探讨

目的 探讨供者KIR分子表达差异对NK细胞杀伤人脐血内皮细胞系ECV304活性的影响,并观察参与杀伤的活化信号通路.方法 RT-PCR及流式细胞仪检测ECV304细胞NKG2D配体MICA/B、ULBP1-3表达,PCR-SSP法行HLA-A、B、Cw分型.自8例健康供者分离外周血NK细胞,流式细胞仪检测KIR2DL1的表达率,LDH释放法测定NK细胞在效靶比20∶1时对ECV304细胞的杀伤活性及anti-KIR2DL1mAb对NK细胞杀伤活性的影响.结果 ECV30细胞在mRNA水平表达MICA/B、ULBP1-3,但在膜蛋白水平均不表达.HLA分型表明,ECV304表达KIR2DL1的配体,而不表达KIR2DL2/3、KIR3DL1的配体.8例健康供者NK细胞KIR2DL1表达率有较大差异,对ECV304细胞的杀伤活性也有不同,双变量相关分析示个体KIR2DL1表达率与NK细胞对ECV304的杀伤率存在负相关(rS=-0.994,P=0.000).anti-KIR2DL1 mAb明显增强NK细胞对ECV304的杀伤活性(t=-4.860,P=0.002).结论 NK细胞对ECV304细胞的杀伤分子机制主要为HLA-KIR信号系统错配,目前已知的NKG2D配体MICMB、ULBP1-3并不参与,这有助于临床活体器官移植时在遗传指导下选择供体.     

Sustained localized expression of ligand for the activating NKG2D receptor impairs natural cytotoxicity in vivo and reduces tumor immunosurveillance

Upregulation of the inducible gene products MICA (human) and Rae-1 (mouse) may promote tumor surveillance and autoimmunity by engaging the activating receptor NKG2D on natural killer (NK) cells and T cells. Nevertheless, sustained expression of MICA by tumors can also elicit NKG2D downregulation, perhaps indicating 'immunoevasion'. Investigating this paradox, we report here that constitutive Rae-1epsilon transgene expression in normal epithelium elicited local and systemic NKG2D downregulation, generalized but reversible defects in NK cell-mediated cytotoxicity and mild CD8(+) T cell defects. The extent of NKG2D downregulation correlated well with the incidence and progression of cutaneous carcinogenesis, emphasizing the utility of NKG2D as a marker of tumor resistance. Thus, NKG2D engagement is a natural mediator of immunosurveillance, which can be compromised by locally sustained ligand expression but potentially restored by innate immune activation.     

NKG2D ligands expression and NKG2D-mediated cytotoxicity in human laryngeal squamous carcinoma cells

The NKG2D is an activating immunoreceptor expressed by NK cells and CD8⁺ T cells. Engagement of NKG2D by its ligands is critical for both innate and adoptive immunity. While the overexpression of NKG2D ligands on certain tumour cells has previously been demonstrated, little is known about NKG2D ligand expression on human laryngeal tumour cells. In this study, we first verified that the interaction between NKG2D and its ligands was critical for NK cell-based immune response to human laryngeal squamous carcinoma cells Hep-2. This NKG2D-mediated effect was observed by transfecting the recombinant eukaryotic expression vector pEGFP-N1/NKG2D as well as the NKG2D blockade. The mRNA and protein expression of NKG2D ligands, MHC class I-related chain molecules A (MICA) and UL16-binding proteins (ULBPs), in human laryngeal carcinoma cell line Hep-2 and fresh tumour tissues were evaluated. Compared with non-tumour tissues of vocal cords polyps, MICA and ULBP-3 were strongly overexpressed on both the human laryngeal carcinoma cell line Hep-2 and fresh human laryngeal carcinoma tissues. The mechanism and impact of NKG2D ligands overexpression on NK cell-mediated anti-laryngeal cancer immune response would require further investigation.     

IL-2-activated haploidentical NK cells restore NKG2D-mediated NK-cell cytotoxicity in neuroblastoma patients by scavenging of plasma MICA

NK group 2D (NKG2D)-expressing NK cells exhibit cytolytic activity against various tumors after recognition of the cellular ligand MHC class I chain-related gene A (MICA). However, release of soluble MICA (sMICA) compromises NKG2D-dependent NK-cell cytotoxicity leading to tumor escape from immunosurveillance. Although some molecular details of the NKG2D-MICA interaction have been elucidated, its impact for donor NK (dNK) cell-based therapy of solid tumors has not been studied. Within an ongoing phase I/II trial, we used allogeneic IL-2 activated dNK cells after haploidentical stem cell transplantation for immunotherapy of patients with high-risk stage IV neuroblastoma. NKG2D levels on activated dNK cells increased strongly when compared with freshly isolated dNK cells and correlated with enhanced NK-cell cytotoxicity. Most importantly, elevated sMICA levels in patients plasma correlated significantly with impaired dNK-cell-mediated cytotoxicity. This effect could be reversed by high-dose infusion of activated dNK cells, which display high levels of surface NKG2D. Our data suggest that the provided excess of NKG2D leads to clearance of sMICA and preserves cytotoxicity of dNK cells via non-occupied NKG2D. In conclusion, our results identify this tumor immune escape mechanism as a target to improve immunotherapy of neuroblastoma and presumably other tumors.     

Contact inhibition causes strong downregulation of expression of MICA in human fibroblasts and decreased NK cell killing

The polymorphic MICA gene encodes glycoproteins that activate T cells and NK cells through the NKG2D receptor and may costimulate immune functions. We found that MICA was expressed on freshly isolated human fibroblasts and was markedly decreased when fibroblasts were grown to confluency in culture dishes. MICA surface protein was measured by flow cytometry with the MICA-specific monoclonal antibody (mAb) 6B3, and HLA class I-specific protein was determined with mAb w6/32. In these experiments, after culture for 120 hours, the staining for MICA in fibroblasts decreased to about 20% of the initial amount and MICA mRNA fell in parallel, while HLA class I staining was maintained or even became somewhat stronger. In other experiments, MICA expression was not decreased when fibroblast contact was prevented by the addition of 1 muM Rottlerin, a specific inhibitor of protein kinase C delta known to prevent contact inhibition of fibroblasts. In the NK cell cytotoxicity assay, blocking MICA by antibody or downregulation by cell contact resulted in a decrease of specific killing by 30%. Increased MICA expression during proliferation of fibroblasts may support the host response to injury.     

Estrogen upregulates MICA/B expression in human non-small cell lung cancer through the regulation of ADAM17

Estrogen is involved in promoting lung cancer cell division and metastasis. MICA and MICB function as ligands for NKG2D, an important immunoreceptor expressed on natural killer (NK) cells. However, whether estrogen regulates MICA/B expression and affects tumor immune escape remains unknown. In this study, we measured the mRNA levels of MICA, MICB and ADAM17in non-small cell lung cancer (NSCLC) cell lines treated with estrogen. Surface expression of MICA/B on LTEP-a2 and A549 was detected using flow cytometry. We demonstrate that both mRNA and secretory protein levels of MICA/B in lung adenocarcinoma cell lines were upregulated by estradiol. Estradiol enhanced the expression of ADAM17, which was associated with the secretion of MICA/B. This secretion of MICA/B downregulated the NKG2D receptor on the surface of NK92 cells and impaired the cytotoxic activity of NK cells. Estradiol enhanced the expression of ADAM17, which was associated with the secretion of MICA/B. Furthermore, a significant correlation between the concentration of estradiol and the expression of MICA was found in tumor tissues of NSCLC patients. Therefore, we conclude that estrogen can regulate the expression and secretion of MICA/B through ADAM17, which helps lung cancer cells escape NKG2D-mediated immune surveillance.     

c‐Cbl regulates MICA‐ but not ULBP2‐induced NKG2D down‐modulation in human NK cells

The NKG2D activating receptor on human NK cells mediates “altered self” recognition, as its ligands (NKG2DLs) are upregulated on target cells in a variety of stress conditions. Evidence collected in the past years shows that, even though expression of NKG2DLs acts as a danger signal that renders tumor cells susceptible to cytotoxicity, chronic exposure to soluble or membrane‐bound NKG2DLs can lead to down‐modulation of receptor expression and impairment of NKG2D‐mediated cell functions. Here, we evaluated whether different cell‐bound NKG2DLs, namely MICA and ULBP2, are equivalently able to induce NKG2D down‐modulation on human NK cells. We found that although both ligands reduce NKG2D surface expression, MICA promotes a stronger receptor down‐modulation than ULBP2, leading to a severe impairment of NKG2D‐dependent NK‐cell cytotoxicity. We also provide evidence that the ubiquitin pathway and c‐Cbl direct MICA‐induced but not ULBP2‐induced NKG2D internalization and degradation, thus identifying a molecular mechanism to explain the differential effects of MICA and ULBP2 on NKG2D expression. A better understanding of the molecular mechanisms employed by the different NKG2DLs to control NKG2D surface expression could be useful for the development of anti‐tumor strategies to restore a normal level of NKG2D receptors on human NK cells.     

NK cell‐mediated anti‐leukemia cytotoxicity is enhanced using a NKG2D ligand MICA and anti‐CD20 scfv chimeric protein

NK cells are important innate cytotoxic lymphocytes that have potential in treatment of leukemia. Engagement of NKG2D receptor on NK cells enhances the target cytotoxicity. Here, we produced a fusion protein consisting of the extracellular domain of the NKG2D ligand MICA and the anti‐CD20 single‐chain variable fragment (scfv). This recombinant protein is capable of binding both NK cells and CD20⁺ tumor cells. Using a human NKG2D reporter cell system we developed, we showed that this fusion protein could decorate CD20⁺ tumor cells with MICA extracellular domain and activate NK through NKG2D. We further demonstrated that this protein could specifically induce the ability of a NK cell line (NKL) and primary NK cells to lyse CD20⁺ leukemia cells. Moreover, we found that downregulation of surface HLA class I expression in the target cells improved NKL‐mediated killing. Our results demonstrated that this recombinant protein specifically lyses leukemia cells by NK cells, which may lead to development of a novel strategy for treating leukemia and other tumors.